Scroll type compressor

ABSTRACT

A scroll type compressor has a fixed scroll member and a movable scroll member. The fixed scroll member has a fixed scroll base plate and a fixed scroll wall extending from the fixed scroll base plate. The movable scroll member has a movable scroll base plate and a movable scroll wall extending from the movable scroll base plate. The fixed scroll member and the movable scroll member cooperatively form a compression region. The movable scroll member orbits relative to the fixed scroll member to compress refrigerant in the compression region. Each scroll wall is formed in a taper shape from each base plate toward each distal end of the scroll wall. The distal end is non-contact with the opposing scroll base plate. Clearance between the distal end and the opposing scroll base plate is less than or equal to the limit clearance value which maintains airtight performance.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a scroll type compressor andmore particularly to structure of a fixed scroll member and a movablescroll member which constitute a compression mechanism in a voluteshape.

[0002] In general, the scroll type compressor has a housing in which thefixed scroll member and the movable scroll member are provided. Thefixed scroll member has a fixed scroll base plate and a fixed scrollwall that extends from the fixed scroll base plate. The movable scrollmember has a movable scroll base plate and a movable scroll wall thatextends from the movable scroll base plate. Each scroll wall is engagedwith each other. The fixed scroll member and the movable scroll membercooperatively form a plurality of compression chambers as a compressionregion. As the movable scroll member orbits about an axis of the fixedscroll member, the compression chambers move radially inward while theirvolume decreases.

[0003] Since bending moment is applied to each scroll wall by highpressure generated in the compression chambers due to the compressionperformance, the bending moment deforms each scroll wall. Therefore,clearance between the scroll walls is increased and compressed fluidleaks through the clearance.

[0004] Accordingly, high compression performance is not obtained.

[0005] To obtain the high compression performance by preventing thecompressed fluid from leaking, as shown in FIG. 4A, a scroll wall 1 wasconventionally created in a taper shape from a joining portion to a baseplate 2 toward a distal end of the scroll wall 1.

[0006] Still referring to FIG. 4A, in the above constitution, the scrollwall 1 is strengthened against bending moment. Therefore, clearancebetween the scroll walls 1 was effectively restrained from increasing.There, such a constitution was employed that a tip seal 3 slides thesurface of the opposing base plate 2 to ensure sealing performance inthe clearance between the distal end of the scroll wall 1 and theopposing base plate 2.

[0007] However, as it is taken into consideration that the compressorused in high speed vehicles is nowadays required to be compact andlightweight for its fuel efficiency, the following problem has occurredin the above prior art. The thickness of the scroll wall 1 is increasedwhen the tip seal 3 is used. As a result, configuration of thecompressor is increased in size.

[0008] As shown in FIG. 4A, when the distal end of the scroll wall 1 isprovided with the tip seal 3, thickness c of the distal end of thescroll wall 1 is determined as follows. c=a+2*b where width of the tipseal 3 is expressed by a, and thickness of an outer wall of a grooveformed in the distal end is expressed by b. Thickness of the portionjoining to the scroll wall 1, which is expressed by d, is alsodetermined to be relatively thick due to increase of the thickness c.

[0009] On the contrary, as shown in FIG. 4B, when the distal end of thescroll wall 1 has similar thickness to the width a of the tip seal 3 insize, thickness e of the portion joining to the base plate 2 becomesrelatively small. Accordingly, the compressor including the scroll wall1 shown in FIG. 4A, has less capacity in the compression chambers thanthat of FIG. 4B, because of an increase in thickness of the scroll wall1 provided with the tip seal 3. To maintain the capacity in thecompression chambers, the configuration of the compressor is inevitablyincreased in size.

SUMMARY OF THE INVENTION

[0010] The present invention addresses a scroll type compressor which ishard, compact and lightweight with high quality sealing performance.

[0011] According to the present invention, A scroll type compressor hasa fixed scroll member and a movable scroll member. The fixed scrollmember has a fixed scroll base plate and a fixed scroll wall extendingfrom the fixed scroll base plate. The movable scroll member has amovable scroll base plate and a movable scroll wall extending from themovable scroll base plate. The fixed scroll member and the movablescroll member cooperatively form a compression region. The movablescroll member orbits relative to the fixed scroll member to compressrefrigerant in the compression region. Each scroll wall is formed in ataper shape from each base plate toward each distal end of the scrollwall. The distal end is non-contact with the opposing scroll base plate.Clearance between the distal end and the opposing scroll base plate isless than or equal to the limit clearance value which maintains airtightperformance between the distal end and the opposing scroll base plate.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The features of the present invention that are believed to benovel are set forth with particularity in the appended claims. Theinvention together with objects and advantages thereof, may best beunderstood by reference to the following description of the presentlypreferred embodiments together with the accompanying drawings in which:

[0013]FIG. 1 is a diagram in a cross-sectional view illustrating a firstpreferred embodiment of the scroll type compressor according to thepresent invention;

[0014]FIG. 2 is a diagram in a partial enlarged view illustrating firstand second preferred embodiments of the scroll type compressor accordingto the present invention;

[0015]FIG. 3 is a graph illustrating a relation between clearance in thedirection of an axis and a ratio of COP according to the presentinvention;

[0016]FIG. 4A is a diagram in a partial cross-sectional viewillustrating a scroll wall with a tip seal according to the prior art;and

[0017]FIG. 4B is a diagram in a partial cross-sectional viewillustrating a scroll wall without a tip seal according to the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] A scroll type compressor according to a first preferredembodiment of the present invention will be described with reference toFIGS. 1 through 3.

[0019] As shown in FIG. 1, a front housing 30, a center housing 31 and arear housing 32 are connected to form a configuration of the compressor.A fixed scroll member 35 is integrally formed with the center housing31. The fixed scroll member 35 has a fixed scroll base plate 33 and afixed scroll wall 34 that extends from the fixed scroll base plate 33.An inlet 36 for introducing refrigerant is also formed in the centerhousing 31 and is connected to an external refrigerant circuit. Amovable scroll member 39 is accommodated in a space defined by thecenter housing 31 and the front housing 30. The movable scroll member 39has a movable scroll base plate 37 and a movable scroll wall 38 thatextends from the movable scroll base plate 37. The fixed scroll wall 34and the movable scroll wall 38 engage with each other. Thereby, aplurality of compression chambers 40 is defined as a compression regionbetween the fixed scroll member 35 and the movable scroll member 39. Adischarge hole 42 is formed substantially at the center of the fixedscroll base plate 33. Compressed refrigerant in the compression chambers40 is discharged into a discharge chamber 41 defined between the centerhousing 31 and the rear housing 32 through the discharge hole 42. Anoutlet 43 is formed in the rear housing 32 to flow refrigerant in thedischarge chamber 41 into the external refrigerant circuit.

[0020] Still referring to FIG. 1, one end of a drive shaft 45 isrotatably supported in the front housing 30 by bearing 44 and the otherend of the drive shaft 45 extends outside of the configuration of thecompressor. A crankshaft 46 is mounted on one end of the drive shaft 45.The crankshaft 46 is received by a bushing 47, which is inserted in aboss 48 of the movable scroll member 39. A self rotation preventingmechanism 49 prevents the movable scroll member 39 from rotating aboutits axis, while allowing the movable scroll member 39 to orbit about anaxis of the fixed scroll member 35.

[0021] As shown in FIG. 2, the fixed scroll wall 34 and the movablescroll wall 38 are respectively formed in a taper shape from portionsjoining to the scroll base plates 33 and 37 toward the respective distalends. The fixed scroll wall 34 has a pair of side surfaces 34 a and 34 bwhich incline by angles of θ₁ and θ₂ with respect to the direction of anaxis of the drive shaft 45 (which is perpendicular to the scroll baseplates 33 and 37), respectively. In a similar manner, the movable scrollwall 38 has a pair of side surfaces 38 a and 38 b which incline byangles of θ₃ and θ₄ with respect to the direction of the axis of thedrive shaft 45 (which is perpendicular to the scroll base plates 33 and37), respectively. At this time, the side surfaces 34 b and 38 a whichface each other are equal in inclination angle. That is, θ₂ equals θ₃.In a similar manner, the side surfaces 34 a and 38 b which face eachother are also equal in inclination angle. That is, θ₁ equals θ₄. Inaddition, when the side surfaces 34 a and 34 b of the fixed scroll wall34 are equal in inclination angle, θ₁ equals θ₂. In a similar manner,when the side surfaces 38 a and 38 b of the movable scroll wall 38 areequal in inclination angle, θ₃ also equals θ₄. In this case, the fixedscroll wall 34 and the movable scroll wall 38 are equal in inclinationangle. The above inclination angle is formed not only by cutting butalso by utilizing a draft upon casting.

[0022] Still referring to FIG. 2, when the compressor is assembled byengaging the movable scroll member 39 with the fixed scroll member 35,the distal end of the fixed scroll wall 34 and the opposing surface ofthe movable scroll base plate 37 are maintained to have clearance G₁therebetween so as not to contact with each other. In a similar manner,the distal end of the movable scroll wall 38 and the opposing surface ofthe fixed scroll base plate 33 are maintained to have clearance G₂therebetween so as not to contact with each other. The clearance G₁generally equals the clearance G₂.

[0023] Now, a method for searching the optimal value of the clearance G₁and G₂ will be explained with reference to FIG. 3. In this graph thevalue of x-axis represents length of clearance G₁ and G₂ in thedirection of the axis expressed by unit of micrometer or μm and thevalue of y-axis represents a ratio of Coefficient of Performance or COPof a compressor according to the present invention, which is notprovided with the tip seal, to that of a compressor which is providedwith the tip seal. In both cases that oil circulating inside exists anddoesn't exist, relation between the length of clearance and the ratio ofCOP is respectively drawn by line graph. Even in the case that thedistal end is provided with the tip seal, the length of the clearancerepresents distance between the distal end of the scroll wall and theopposing surface of the scroll base plate.

[0024] Still referring to FIG. 3, note that efficiency of load L whichis required due to a heat absorption in an evaporator is generallyexpressed by COP as follows. COP=Q_(er)/L, where Q_(er) denotesefficiency of refrigeration.

[0025] In view of total performance of the compressor, the ratio of COPis allowable if it is more than or equal to 0.9. At this time, in thecase that the oil circulating inside exists, FIG. 3 reads that thelength of the clearance is less than or equal to 60 μm. In the case thatno oil circulating inside exists, FIG. 3 reads that the length of theclearance is less than or equal to 47 μm. Accordingly, it is requiredthat the clearance G₁ and G₂ are each less than or equal to the aboveupper limit value.

[0026] Then, function of the first preferred embodiment will beexplained. As shown in FIG. 1, when the drive shaft 45 that extendsoutside of the configuration of the compressor is rotated by drivingforce of an external drive source such as a vehicle engine, which isconnected to the drive shaft 45 through a pulley which is not shown, themovable scroll member 39 orbits about the axis of the fixed scrollmember 35. Refrigerant gas introduced from the external refrigerantcircuit through the inlet 36 is compressed to be predetermined pressurein the compression chambers 40 and discharged into the discharge chamber41 through the discharge hole 42 by the orbital movement. Thepressurized refrigerant gas discharged into the discharge chamber 41 issent to the external refrigerant circuit through the outlet 43.

[0027] As shown in FIG. 2 in combination with FIG. 1, during the abovecompression process, bending moment is applied to the scroll walls 34and 38 due to compression movement in the compression chambers 40. Inthis constitution, however, the fixed scroll wall 34 and the movablescroll wall 38 are respectively formed in a taper shape from theportions joining to the scroll base plates 33 and 37 toward therespective distal ends, while having relatively sufficient thickness ofthe portions. Accordingly, the fixed scroll wall 34 and the movablescroll wall 38 are restrained from being deformed, thus effectivelymaintaining a sealing performance therebetween.

[0028] Still referring to FIG. 2, while the distal ends of the fixedscroll wall 34 and the movable scroll wall 38 are not in contact withthe respective opposing surfaces of the movable scroll base plate 37 andthe fixed scroll base plate 33, sealing performance is respectivelyensured since the distance therebetween is less than or equal to theupper limit clearance value which maintains airtight performance. Thus,total sealing performance in the compression region is relatively andsufficiently maintained. Therefore, high compressing performance isobtained. Besides, since the distal ends of the scroll wall 34 and 38and the respective opposing surfaces of the scroll base plates 37 and 33are prevented from directly contacting, power loss is also restrained tobe extremely small while the compressor is driven.

[0029] Especially, as shown in FIG. 3 in combination with FIG. 1, in thecase that the oil circulating inside exists when the clearance in thedirection of the axis of the drive shaft 45 is less than or equal to 36μm, the ratio of COP is more than or equal to 1. In a similar manner, inthe case that no oil circulating inside exists when the clearance in thedirection of the axis of the drive shaft 45 is less than or equal to 30μm, the ratio of COP is also more than or equal to 1. These mean thatthe compressor according to the present invention has superiorefficiency of refrigeration to the compressor provided with the tip sealwhen the clearance G₁ and G₂ are less than or equal to the foregoingupper limit value. This is regarded because the compressor provided withthe tip seal losses power due to sliding friction generated between thetip seal and the opposing surface of the scroll base plate. Accordingly,in the above description while the clearance G₁ and G₂ are less than orequal to 60 μm, more preferably, in the case that the oil circulatinginside exists, the clearance G₁ and G₂ are less than or equal to 36 μm.In a similar manner, while the clearance G₁ and G₂ are less than orequal to 47 μm, more preferably, in the case that no oil circulatinginside exists, the clearance G₁ and G₂ are less than or equal to 30 μm.

[0030] Referring back to FIG. 2, in this embodiment, since the distalends of the scroll walls 34 and 38 are not provided with the tip seal,while provided in the prior art, the thickness of the distal ends of thescroll walls 34 and 38 is prevented from inevitably increasing byproviding the tip seal. Accordingly, the thickness of the scroll wall isdetermined to be minimized. In spite of the relatively sufficientthickness of the joint portion, the configuration of the compressor isnot increased in size.

[0031] In this embodiment the following effects are obtained. Firstly,still referring to FIG. 2, since the scroll walls 34 and 38 arerestrained from being deformed to resist to bending moment by relativelyand sufficiently ensuring the thickness of the joint portions of thescroll walls 34 and 38, sealing performance is ensured. In addition,sealing performance is also ensured in clearance between the distal endsof the scroll walls 34 and 38, and the respective opposing surfaces ofthe scroll base plates 37 and 33. As a result, total sealing performancein the compression region is relatively and sufficiently maintained.Thus, high compressing performance is obtained.

[0032] Secondly, since sealing performance is sufficiently ensuredtherebetween while the distal ends of the scroll walls 34 and 38 are notin contact with the respective opposing surfaces of the scroll baseplates 37 and 33, relatively sufficient efficiency of compression isensured by the distal ends of the scroll walls 34 and 38 with necessaryminimal thickness, and the scroll walls 34 and 38, as a whole, havenecessary minimal thickness. Accordingly, capacity in the compressionregion is increased, and in its turn, the compressor is, as a whole,reduced in size and weight.

[0033] Thirdly, the side surface 34 a of the scroll wall 34 and the sidesurface 38 b of the scroll wall 38 facing each other are equal ininclination angle. Also, the side surface 34 b of the scroll wall 34 andthe side surface 38 a of the scroll wall 38 facing each other are equalin inclination angle. Therefore, airtight constitution in thecompression region is easily obtained by a draft upon casting. Inaddition, the side surfaces 34 a and 34 b of the scroll wall 34 are eachequal in inclination angle. Also, the side surfaces 38 a and 38 b of thescroll wall 38 are equal in inclination angle. Moreover, since theseside surfaces 34 a, 34 b, 38 a and 38 b are each set to be equal ininclination angle even between the scroll members 35 and 39, molding forcasting is easily manufactured.

[0034] Fourthly, since the inclination angles of the side surfaces 34 a,34 b, 38 a and 38 b of the scroll walls 34 and 38 are formed byutilizing a draft upon casting, cutting process is not required.Therefore, person-hour for manufacturing is reduced. In addition, sincecasting surface or surface as forged is used in this case, thecompressor which is high in surface hardness and durability is obtained.

[0035] A scroll type compressor according to a second preferredembodiment of the present invention will be described with reference toFIG. 2. In this embodiment, the side surfaces 34 a, 34 b of the scrollwall 34 are different in inclination angle. Also, the side surfaces 38a, 38 b of the scroll wall 38 are different in inclination angle. Thatis, inclination angles θ₁, θ₂ of the side surfaces 34 a, 34 b of thescroll wall 34 are different from each other. Also, inclination anglesθ₃, θ₄ of the side surfaces 38 a, 38 b of the scroll wall 38 aredifferent from each other. However, the side surfaces 34 a, 38 b and 34b, 38 a of the scroll walls 34 and 38 which are facing each other areequal in inclination angle. That is, the relation between θ₁, θ₂, θ₃ andθ₄ is expressed as follows. θ₂=θ₃. θ₁=θ₄.

[0036] As described above, side surfaces of a scroll wall are differentin inclination angle. When the scroll member is formed, for example, bycasting, it may be required that the side surfaces of the scroll wallare different in draft in a casting plan. Accordingly, inclinationangles of the side surfaces predetermined differently. The otherconstitution of the second embodiment is similar to the constitution ofthe first embodiment, and the overlapped explanation is omitted.

[0037] As constituted above, since each pair of side surfaces 34 a, 38 band 34 b, 38 a of the scroll walls 34 and 38 facing each other is equalin inclination angle even if the side surfaces 34 a, 34 b and 38 a, 38 bof the scroll walls 34 and 38 are each different in inclination angle,sealing performance in the compression chambers 40 is ensured. Thus,compression cycle in the compression chambers 40 is performed withoutobstruction.

[0038] In this embodiment, the above described effects of the firstembodiment are obtained. In addition, the following effect is alsoobtained.

[0039] Since it is possible that each side surface of the scroll wall ofthe scroll member is different in inclination angle, a design in acasting plan is relatively freely performed. As a result, the scrollmember is easily manufactured.

[0040] In the present invention, the following embodiment is alsopracticed. The scroll type compressor according to the above embodimentshas the drive shaft which protrudes outside of the configuration of thecompressor and is operatively connected to the external drive sourcesuch as an engine. However, the above external drive source may be builtin type or canned motor type. That is, electric motor for driving thedrive shaft may be installed in the compressor.

[0041] As described above, in the present invention, since thickness ofthe joint portion of the scroll wall is larger than that of the distalend of the scroll wall, the scroll wall is prevented from beingdeformed. In addition, sealing performance is ensured in clearancebetween the distal end of the scroll wall and the opposing surface ofthe scroll base plate. Therefore, airtight performance in thecompression region is, as a whole, maintained. As a result, highcompressing performance is obtained. Moreover, since the distal end isnot provided with the tip seal, the scroll wall has, as a whole,relatively small thickness. As a result, the scroll wall becomes compactand lightweight. Thus, various prominent effects are obtained.

[0042] The present examples and preferred embodiments are to beconsidered as illustrative and not restrictive and the invention is notto be limited to the details given herein but may be modified within thescope of the appended claims.

What is claimed is:
 1. A scroll type compressor comprising: a fixedscroll member having a fixed scroll base plate and a fixed scroll wallextending from the fixed scroll base plate; and a movable scroll memberhaving a movable scroll base plate and a movable scroll wall extendingfrom the movable scroll base plate, wherein the fixed scroll member andthe movable scroll member cooperatively form a compression region, andwherein the movable scroll member orbits relative to the fixed scrollmember to compress refrigerant in the compression region, and whereineach scroll wall is formed in a taper shape from each base plate towardeach distal end of the scroll wall, the distal end being non-contactwith the opposing scroll base plate, clearance between the distal endand the opposing scroll base plate being less than or equal to the limitclearance value which maintains airtight performance between the distalend and the opposing scroll base plate.
 2. The scroll type compressoraccording to claim 1 wherein the side surface of the fixed scroll walland the side surface of the movable scroll wall, which are facing eachother, have an equal inclination angle with respect to the direction ofan axis which is perpendicular to the base plate.
 3. The scroll typecompressor according to claim 2 wherein the side surfaces of the fixedscroll wall and the movable scroll wall have an equal inclination anglewith respect to the direction of the axis.
 4. The scroll type compressoraccording to claim 1 wherein the limit clearance value is less than orequal to 60 μm when circulating oil exists in the compression region. 5.The scroll type compressor according to claim 4 wherein the limitclearance value is less than or equal to 36 μm.
 6. The scroll typecompressor according to claim 1 wherein the limit clearance value isless than or equal to 47 μm when no circulating oil exists in thecompression region.
 7. The scroll type compressor according to claim 6wherein the limit clearance value is less than or equal to 30 μm.
 8. Thescroll type compressor according to claim 1 wherein each scroll wall isformed in a taper shape from each base plate toward each distal end ofthe scroll wall by utilizing a draft upon casting.
 9. A scroll fluidmachine comprising: a fixed scroll member having a fixed scroll baseplate and a fixed scroll wall extending from the fixed scroll baseplate; and a movable scroll member having a movable scroll base plateand a movable scroll wall extending from the movable scroll base plate,wherein the fixed scroll member and the movable scroll membercooperatively form a compression region, and wherein the movable scrollmember orbits relative to the fixed scroll member to compress fluid inthe compression region, and wherein each scroll wall is formed in ataper shape from each base plate toward each distal end of the scrollwall, the distal end being non-contact with the opposing scroll baseplate, clearance between the distal end and the opposing scroll baseplate being less than or equal to the limit clearance value whichmaintains airtight performance between the distal end and the opposingscroll base plate.